ROLE OF ABIOTIC ENVIRONMENTAL FACTORS IN THE DEVELOPMENT OF FRENCH BEAN RUST AND ITS MANAGEMENT
Loading...
Date
2018-05-19
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
UHF,NAUNI
Abstract
ABSTRACT
Rust is an important disease of French bean particularly of pencil types in mid hills of Himachal
Pradesh. Present investigations were undertaken during 2015 and 2016 crop seasons with an objective to study
the occurrence of the disease, role of abiotic environmental factors in disease development and to devise suitable
disease management strategies. The disease was found to occur in moderate to severe form in major French
bean growing areas of Himachal Pradesh. The samples collected from different locations were found infected
with urediniospores. On the basis of morphological characters like shape, size, colour and echinulation of the
urediniospores and molecular characterization the associated fungus was identified as Uromyces appendiculatus
(Pers.) Unger). Pathogenicity of the associated pathogen was proved with 7 days incubation period. Among
different substrates evaluated, sucrose was observed to be the best substrate with maximum (62.63%)
urediniospore germination and germtube elongations (168.80 μm). Temperatures of 20°C and pH 7.0 were
observed to be best for the germination and germ tube elongation of urediniospores. Moderate temperature
(20ºC) and high humidity (>85%) were found to be most congenial factors for disease development, whereas
high rainfall was deleterious to the disease development. Diurnal periodicity of spore release indicated that
release of urediniospores was continuous throughout the day and night but 72.46 per cent of the total daily spore
load was recorded in between 08:00 and 16:00 h. Among sixty six different germplasm lines/cvs./local
selections screened against pathogen, thirty one genotypes were found to be highly resistant under natural
epiphytotic and artificial inoculation conditions. Based on different components of slow rusting, five lines viz.,
EC-755318, EC-400442, EC-400406, EC-400390 and EC-405210 were recorded as slow rusters. Minimum rust
severity and maximum green pod yield was recorded in 45×15 cm spacing as compared to other plant spacings.
Under in vitro conditions mancozeb was found to be the best fungicide followed by chlorothalonil and
tebuconazole + trifloxystrobin. Foliar sprays of azoxystrobin (0.1%) were found most effective both in reducing
the rust severity and increasing the green pod yield followed by tebuconazole + trifloxystrobin and azoxystrobin
+ difenconazole. Azoxystrobin, EBIs and mancozeb exhibited good protective activity of 120 h, and 72 h,
respectively, while only EBIs demonstrated excellent post infection (72 h) and pre symptoms activity. These
fungicides also triggered the activity of defense related enzymes (PO, PPO and PAL) in bean plants upon
challenge inoculation. Among different botanicals evaluated, Neemazal and A. stavium caused maximum
urediniospore germination inhibition under in vitro conditions. In integrated disease management, 45×15 cm
spacing + azoxystrobin was most effective in reducing the rust severity (4.39%) and increasing the green pod
yield (9.46 kg/plot).
Description
Keywords
null